Moved to Helix forum
BMC offers Helix Remedy in their own data center or on their instances of AWS and Azure; customers can choose the preferred environment.
I don't know if other companies are offering Helix Remedy in the same way.
I don't know what SAP and others do; in the case of BMC, customers get a Helix Remedy environment that is their own, they don't get a slice of an environment that others are using.
Yes, you can install on premise Remedy into AWS or Azure. I haven't done it, but I've had customers do it. Hopefully someone else can offer you "real world" experience!